Process for fibers containing uniform distribution of insoluble solid additives therein

ABSTRACT

A PROCESS FOR PREPARING FIBERS WHICH COMPRISES (A) PREPARING A POLYMER SOLUTION IN A SOLVENT THEREFOR, (B) PREPARING A SOLUTION OF A SOLID PROPERTY-MODIFYING ADDITIVE IN AN ORGANIC LIQUID WHICH IS INSOLUBLE IN THE POLYMER SOLUTION, (C) DISPERSING THE ADDITIVE SOLUTION AND POLYMER SOLUTION BY HIGH SHEAR MIXING, (D) IMMEDIATELY WET SPINNING THE DISPERSION INTO FIBER, AND (E)THEREAFTER REMOVING SAID ORGANIC LIQUID FROM THE FORMED FIBER BY EVAPORATION OR WASHING TO LEAVE A UNIFORM DISTRIBUTION OF INSOLUBLE SOLID PROPERTY-MODIFYING ADDITIVE IN THE FIBER.

niformdispersion'in the spinning solution spinning the resulting mixture.

United States Patent i 3,773,884 PROCESS. FOR: FIBERS CONTAINING UNIFORM z,n-DISTRIBUTION .OF INSOLUBLE SOLID ADDI- TIVES. THEREIN Yukio,Shi mosaka and Yoshihiro Uno, Okayama, Japan,

z'ssignors to American Cyanamid Company, Stamford,

onn.

No Drawing. Continuation-impart of abandoned applica- 'tiou Ser. No. 99,517, Dec, 18, 1970. This application Apr. 7,1972, Ser. No. 242,249 Claims priority, application Japan, Dec. 20, 1969, 44/102,826 Int.'Cl. D01f 7/00 U.S. 'Cl.---264- -182 10 Claims ABSTRACT oF DISCLOSURE process'for' preparing fibers which comprises (a) preparing a polymer solution in a solvent therefor, (b) preparing a solution of a solid property-modifying additive in an organic liquid which is insoluble in the polymer solution, (0) dispersing the additive solution and polymer solution by .high shearmixing, ((1) immediately wet spinningthe dispersion into fiber, and (e) thereafter removing said'organic liquid from the formed fiber by evaporation or washing to leave auniform distribution of insoluble solid property-modifying.additive in the fiber.

.This application is a continuation-in-part of application Sen-No. 99,517, filed Dec. 18, 1970, and now abandoned.

This invention relates. to a process for preparing fiber containing uniformly distributed therein insoluble solidproperty-modifying additive. More particularly, this invention relatesto such a process wherein the solid property-modifying additive is dissolved in an organic liquid which can readily be removed from the formed fiber by volatilization or washing so as to leave the solid additive uniformlydistributed within the fiber, said additive being insoluble with respect to subsequent conventional fiber processing.

.It has long been known that various additives can be [incorporated into viscous spinning solutions used to form fibers and filaments by coagulation of polymers in such 7 solutions and that the resulting products have modified 1 characteristics by virtue of the additive thus employed.

The usual additives include, for example, titanium dioxide, frosting agents, pigments, lustering agents, ultraviolet absorbers, and'resins. The usual method of adding such f'solid additives to a highly viscous spinning solution comfprises finely dividing such solid by means of a colloid mill or the like'and dispersing such finely divided solid in the polymer solution by use of an agitator, a crusher, a kneadtion of the spinning solution to form a concentrate and then adding the concentrate to a far larger amount of --spinning solution just prior to coagulation thereof. Al-

tough this; method is improved, over the former, there still remains some of the deficiencies of the former metha manner whereby the solid additive isprecipitated as a and then wet etan'other. method is to dissolve. the solid additives in a' solvent miscible with 'the spinning solution,

additive solution with the spinning solution ent mveniioa-usetu polymers Include polyemides', e

nylons; polyesters, e.g. polytethylen'eg lycolt Li -{vinyl polymers, 5e

The above method, however, causes such undesirable "Ice phenomena as gelling the spinning solution and render ing it incapable of being spun. In effect, the solvent used in preparing the additive solution, being different from that used in forming the polymer solution but soluble in said polymer solvent, reduces the capacity of the polymer solvent for polymer and causes gelling of polymerq In accordance with the present invention, there is pro vided a process for preparing fiber containing a unifor'm distribution of insoluble solid property-modifying additive therein, which process comprises: (a) preparing' a solution of a fiber-forming polymer in a solvent there for, said polymer comprising from about 5% to 30%, by weight, based on the total weight of said polymer solution; (b) preparing a solution of a solid property-modifying additive in an inert organic liquid which is insoluble in said polymer solution and capable of being removed from the formed fiber by evaporation, extraction, or washing, said solid additive being insoluble in the polymer and with respect to subsequent fiber processing, the amount of said solid additive present in said organic liquid being up to about 70% by weight based on the total weight of said additive solution; (c) uniformly dispersing said additive solution in said polymer solution by high shear mixing, the amount of polymer in the resulting dispersion being at least 30%, by weight, based on the total weight of polymer and additive therein; (d) immediately wetspinning the dispersion into fiber; and (e) thereafter removing the organic liquid from the fiber by evaporation, extraction, or washing so as to leave a uniform dispersion of insoluble solid property-modifying additive uniform ly distributed within the fiber. In carrying out the process of the present invention, use is made of an organic liquid in forming the additive solution, which liquid is insoluble in the polymer solution so as to avoid gelation of said polymersolution and, at the same time, advantageously enables large amounts of property-modifying additive to be introduced into the blockage of spinnerette orifices with aggregated solid additive. In addition, the solid additive being in uniform distribution in the fiber ultimately obtained provides fiber of excellent properties. The present process enables larger amounts of solid property-modifying additive to be uni formly distributed within the fiber than was heretofore possible and thus provides fiber having a higher degree of property modification from the particular additive than was formerly possible.

The dispersion of polymer solution and additive solution is generally extruded into a coagulating liquid in as short a time period following mixing as is possible to form a filament. This is to ensure that the uniformity of the dispersion achieved by high shear mixing is not adversely affected by unnecessary delay in spinning the dispersion as originally obtained. The coagulating liquid may be any that is conventionally used based on the combination of fiber-forming polymer and polymer solvent employed;

Upon coagulation of the spun fiberand subsequent. operations such as washing, stretching, drying, and heat treatment, both the polymer solvent and the additive solvent are removed from thefiber, the former generally 'by dissolutionupon coagulation andwashing the latter by washing, extraction, or evaporation ,during the appr oprit'e The solid additive distribjlltionire sult s frorn re tal; q i he additive solvent, and the solid additives f vives'fsubsequent fiber processing'st'ep's conventionally em- ;ii y s js 'i e it ns hibl iw resp ct; a su t p Most of the corive'ntionally lknow'n fibei"- f9'rrning polyean'be made into fibers p cess of the presa r fl l Ipo lyvinyl chloride' and polyvinyl al cohol; and acrylic polymers, e.g. polyacrylonitrile and copolymers thereof with one or more vinyl monomers copolymerizable therewith. Suitable solvents for use with such polymers in wet-spinning are well known. A preferred embodiment of the process of the present invention involves use of acrylonitrile polymers and wet-spin- I ning of such polymers dissolved in inorganic salt solutions.

For simplicity, the process of the present invention will be described in terms of this preferred embodiment, although it is to be understood that the invention is not limited thereto.

Numerous spinning solutions containing acrylonitrile polymerization products dissolved in suitable solvents are useful in the process of the present process. For example,

' the polymers and solvents disclosed in US. Pat. No. 2,948,-

581, Cummings, Aug. 9, 1960, and in the various other patents cited therein are useful.

Typical acrylonitrile polymerization products are those containing at least 70%, by weight, based on the total weight of the polymer, of acrylonitrile and the balance of one or more comonomers copolymerizable therewith and containing one CH =C group. Illustrative monomers include, for example: vinyl esters, such as vinyl acetate,

. vinyl propionate, and vinyl butyrate; vinyl halides and vinylidene halides, such as vinyl chloride, vinyl bromide,

7 vinyl fluoride, vinylidene chloride, vinylidene bromide,

and vinylidene fluoride; allyl alcohols, such as allyl alcohol, methallyl alcohol, and ethallyl alcohol; allyl, methallyl, and other unsaturated monohydric alcohol esters of v monobasic acids, such as allyl and methallyl acetates and laurates; acrylic acids and alkacrylic acids, such as acrylic 1 acid, methacrylic acid and ethacrylic acid; esters and j'. amides of the foregoing acids, such as methyl, ethyl,

propyl, and butyl acrylates and methacrylates, acrylamide,

,,methacrylamide, N-methyl, N-ethyl, N-propyl, and N- butyl acrylamides and methacrylamides; methacrylonitrile,

ethacrylonitrile and other hydrocarbon-substituted acrylo- E nitriles; unsaturated sulfonic acids and their salts, such as allylsulfonic acid, methallylsulfonic acid, styrene sulfonic acid and their sodium and potassium salts; unsatuweight of the polymer.

Generally, the molecular weight (average) of a useful acrylonitrile polymer will be in the range of from about 25,000 to about 300,000, and preferably in the range of 50,000 to 100,000. The molecular weight is determined from the viscosity of the polymer in dimethyl formamide and by use of the Staudinger equation (see US. Pat. 2,404,173).

Typical solvents for acrylonitrile polymers include organic solvents such as dimethyl formamide, dimethyl acetamide, ethylene carbonate, and dimethyl sulfoxide, as well as inorganic solvents such as concentrated aqueous solutions of inorganic salts, such as thiocyanate salts, i.e. the sodium and; calcium salts, and zinc chloride, for example.

Preferred solventsfor acrylonitrile polymers are the concentrated aqueous thiocyanate salt solutions. For other fiber-forming polymers, conventional solvents are contemplated. The concentration of polymer in the spinning solution is generally in the range of about to 30%, by

weight based on the total weight of solution. The specific concentration will vary from instance to instance depending upon the temperature and viscosity of the polymer 1' solution to be employed, the nature :of the polymer ,."and

the nature of the polymer solution.

' As to the organic liquid to be used as the additive solvent, it must be substantially insoluble in the polymer 4 solution, i.e. show a solubility therein of preferably less than 0.5% by weight at 50 C. Such organic liquid must also be inert, i.e. does not react with the additive, the polymer solvent or the polymer. The organic liquid, or additive solvent as it is sometimes referred to, should also be capable of being removed from the formed fiber by washing, extraction, or evaporation and leave the insoluble solid additive remaining uniformly distributed within the fiber. The amount of organic liquid to be used in forming the additive solution should be sufficient to effect complete solution of the additive employed at the temperature of use contemplated. By solution as that term is employed herein is meant both a true solution and colloidal solu tion. A true solution is one which is homogeneous both macroscopically and microscopically. A collodial solution, on the other hand, is one which is macroscopically homogeneous but microscopically heterogeneous, exhibiting the Tyndal effect. Such solutions are typical of high molecular weight polymers, for example. The amount of organic liquid used to dissolve solid additives contemplated may be as low as 30% by weight, based on the total weight of additive solution. Stated otherwise, the solid additive may be present in an amount up to about by weight, based on the total weight of the additive solution.

In preferred embodiments, i.e. when a polymer of acrylonitrile is employed in a concentrated aqueous solution of an inorganic salt such as sodium thiocyanate, calcium thiocyanate, zinc chloride, or calcium chloride, for example, a suitable organic liquid is found among aliphatic hydrocarbons, such as n-hexane, n-heptane, n-octane, isopentane, isohexane, and petroleum ether; alicyclic hydrocarbons, such as cyclohexane, methylcyclohexane, and decaline; aromatic hydrocarbons such as benzene, toluene, xylene, ethylbenzene, and amyl naphthalene; hydrocarbon halides, such as trichloroethylene, tetrachloroethylene, carbon tetrachloride, dichloropentane and monochlorobenzene; nitro compounds, such as nitrobenzene; ketones, such as methylhexylketone, diisobutylketone, and methylcyclohexanone; ethers, such as hexylether and Z-ethylhexylether; esters, such as methylamyl acetate, 2-ethylhexyl acetate, and nonyl acetate; alcohols, such as 2-ethylhexanol, n-octanol, and n-decanol; and mixture thereof. The specific organic liquid to be selected will depend upon the specific solid additive to be employed and, of course, the other requirements stated above. In other polymerzsolvent systems contemplated for preparing the spinning solution alternative choices for additive solvent can readily be found, if necessary.

' There are numerous property modifications that can be effected by having solid additives uniformly distributed within fibers. For example, solid additives which act as frosting agents, antioxidants, pigments, lustering agents, ultraviolet absorbers, dye levelers are used. In addition, there may be used solid synthetic polymers, such as polyvinyl chloride, polyvinylidene chloride, polyethylene fluoride, polyethylenes, polypropylenes, nylon-6, nylon-6,6, polyesters; synthetic rubbers, such as NBR, SBR, and butyl rubber, polydimethyl' siloxanes; stabilizers such as Ba-Cd laurate, Sr-Zr laurate, barium' stearate, magnesium stearate, and dibutyl tin maleate; organicpigments, such as benzidine orange, benzidine yellow, copper phthalocyanine green, pyrazolone red and pearl pigments; antistatic agents, such as monoglyceride stearate, sorbitanefldistearate and trimethyloctadecylammonium chloride; softening agents such as octadecylamine acetate'and octadecyleneurea; flame retardants, such as bisphenol tetrabromide, butane tetrabromide, phtholic anhydride tetrabromide, and perchloropentacyclodecane; and antimold agents such as tributyl tin acetate, zinc dimethyldithiocarbamate, salicylanilide and'tetramethylthiuram disulfide.

The particular amount of additive solution to be dispersed inthe polymer'solution will vary widely, depending upon the nature of the property-modifying additive to be employed and the degree of property modification desired.

known and provide the necessary provisions ,thoroughly removing relaxing steps.

The smallest amount of additive employed is only limited by that amount which will exhibit a perceptible and desirable, property modification. The maximum amount of property modifier, or additive, is about"70%,by-weight, based on the total weight of additive and polymer in the dispersion, exclusive of polymer and additive solvents. Higher amounts cause extensive loss of fiber properties in the fiber obtained.

Any high shearing type of agitator may be used to prepare the dispersion of additive solution in the polymer solution. A large variety of such devices are available commercially from a number of manufacturers under a plurality of trade names. Shearing should be sufiicient to prepare a uniform dispersion of sufficient stability to be processed by wet-spinning. Conventional use of the selected high shearing'device is generally suitable for preparing useful dispersions in accordance with the present invention.

f The dispersion of additive solution in the fiber-forming polymer solution is spun into fiber by conventional wet spinning procedures. Such spinning procedures are well for washing, extraction, or evaporation of the additive solvent while the polymer solvent. The invention is further illustrated by the examples which follow in which' all percentages and parts are by weight unless otherwise specifically stated.

EXAMPLE 1 I The polymer solution used to prepare fibers consisted of the following:

The polymer solution and the additive solution were simultaneously fed in a ratio of by volume of 8:1, respectively, by means of an in-line high shear mixer (Pipe Line Homomixer, manufactured by Special Machine Chemical Engineering Co., Japan). The dispersion was then immediately spun into an aqueous coagulation bath containing 12% sodium thiocyanate. The spinnerette contained 50 orifices, each of a diameter of 0.12 millimeter and the coagulation bath was maintained at a temperature of 2 C. The coagulated filament was washed with water, stretched in boiling water at a stretch ratio of :1, and steam-relaxed at 125 C. The fiber underwent 30% shrinkage during relaxation and the fiber obtained was of 2.85 deniers, had a dry strength of 2.07 grams per denier, a dry elongation of 26.8%, a knot strength of 1.90 grams per denier, a knot elongation of 23.7%, and an elasticity of 75% at 3% elongation. A soft fiber of very favorable properties thus resulted and the fiber contained a uniform distribution of 12.7% of the acrylonitrile-butadiene copolymer as an insoluble solid additive therein.

In obtaining the fibers, the polymer solvent was removed in the coagulation and water-washing steps and the toluene was removed during the stretching and steam- EXAMPLE 2 The procedure of Example 1 was repeated in every material detailed except that the stretched fiber was steamrelaxed at 143 C. instead of at 125 C. The fiber underwent 60% shrinkage during relaxation and the fiber obtained was of 4.05 deniers, had a dry strength of 1.53

6 grams per denier, a dry elongation of 45.1%, a knot strength of 1.42 grams per denier, and a knot elongation of 37.9%. A soft fiber of favorable properties was again obtained." 1

' COMPARATIVE EXAMPLE A' The procedure of Example 1 was repeated in every material detail except that as the organic liquid used in the additive solution there was substituted for toluene a 60:40 mixture of benzene:methyl ethyl ketone. The polymer solution gelled when the resulting additive solution was mixed therewith and spinning could not be effected.

EXAMPLE 3 EXAMPLE 4 The polymer solution consisted of 10 parts of a 91:9 acrylonitrilewinyl acetate copolymer dissolved in parts of a 50% aqueous solution of sodium thiocyanate. The additive solution consisted of 30 parts of polyvinyl chloride in 70 parts of trichloroethylene. The additive solution was dispersed in the polymer solution at a ratio of 1:3, respectively, using a high shear in-line mixer (a Pipe Line Mixer manufactured by Shimazaki Manufactory, Japan). The mixture was then immediately extruded into a coagulating bath of 10% aqueous sodium thiocyanate maintained at 0 C. using the same spinnerettes as in Example 1. The coagulated filament was washed in water, stretched and steam-relaxed as in Example 1. The fiber obtained contained 45% of polyvinyl chloride as an insoluble solid additive uniformly distributed throughout the fiber and had excellent flame resistance and other favorable propertie as in Example 1.

The polymer solvent was removed during coagulation and washing and the organic liquid, during heating incident to the stretching step.

COMPARATIVE EXAMPLE B The procedure of Example 4 was followed in every material detail except that no organic liquid was used to prepare a dispersion of the finely-divided solid additive and the additive was added directly to the polymer solution. A uniform dispersion was not obtained. Spinning was constantly interrupted by orifice blocking and breaks constantly occurred in the filaments extruded so that con tinuous spinning could not be maintained. Since filament breakage interfered with necessary subsequent processing, no fiber was obtained.

COMPARATIVE EXAMPLE C The procedure of Example 4 was followed in every material detail except that in place of trichloroethylene there was substituted an equal amount of acetone. The spinning solution gelled during the mixing step and could not be spun.

We claim:

1. A process for preparing acrylic fiber containing a uniform distribution of insoluble solid property-modifying additives therein, which process comprises: (a) preparing a spinning solution of a fiber-forming acrylonitrile polymer in a solvent therefor, said polymer containing at least 70%, by weight, of acrylonitrile and the balance of one or more comonomers copolymerizable therewith and containing one CH =C group and comprising from about 5% to 30%, by weight, based on the total weight of said polymer; (b) preparing a solution of a solid property-modifying additive in an inert organic liquid which is insoluble in said polymer solution and capable of being removed from the formed fiber by washing, extraction, or

evaporation, saidliquid being selected from aliphatic hydrocarbons, alicyclic. hydrocarbons,,aromatic hydrocarbons, hydrocarbon halides, nitro compounds, ethers, esters, alcohols, and mixtures thereof, said solid additive being insoluble in the polymer and with respect to subsequent fiber processing and selected, from frosting agents, antioxidants, pigments, lustering agents, ultraviolet absorbers, dye levele'rs, vsynthetic polymers, synthetic rubbers, stabilizers, organic pigments, antistatic agents, softening agents, flame retardants, and antimold agents, the amount of said 'solid additive present in said organic liquid being up to about 70%, by weight, based on the total weight of said additive solution; (c) uniformly dispersing said additive solution in said fiber-forming acrylonitrile polymer solution by high shear agitation, the amount of polymer in the resulting dispersion being at least 30%, by weight, based on the total weight of polymer and additive therein; (d) immediately wet-spinning the dispersion into fiber; and (e) thereafter removing the organic liquid from the fiber by evaporation, extraction, or washing so as to leave a uniform dispersion of solid property-modifying additive uniformly distributed within the fiber.

2. The process of claim 1 wherein said polymer is an acrylonitrile polymer containing at least about 80% of acrylonitrile, by weight, based on the total weight of the polymer, and the balance of one or more comonomers copolymerizable therewith.

3. The process of claim 2 wherein the polymer solvent is a concentrated aqueous inorganic salt solution.

4. The process of claim 3 wherein the inorganic salt is a thiocyanate salt.

5. The process of claim 4 wherein the polymer is a copolymer of 90% by weight of acrylonitrile and 10% by weight of methyl acrylate.

6. The process of claim 4 wherein the polymer is a copolymer of 91% by weight of acrylonitrile and 9% by;

wherein said additiv'etis polyvinyl chloride. 3

10. The process of claim 9 whereintheior ganic is trichloroethylene.

References Citedv UNITED STATES PATENTS v i Ham 260 898 2,769,792 11/1956 I 2,793,195 5/1957 Vesce '260 29.6 2,908,659 10/1959 Shashoua' 264' l82 2,955,017 10/1960 Boyer 264 -182 3,210,315 10/1965 Blackburn et a1. 2 6O'898 3,257,351 6/1966 Kraus et a1. 260-342 3,384,586 5/1968 McMillen 252-43 3,410,819 11/1968 Kourtz et 211, 260 29.6 AN 3,451,960 6/1969 Schmidt 260-29.6" AN 3,560,423 2/1971 Levesque etval', 260 29;6,AN 3,567,119 3/1971 Wolbert 252752 2 FOREIGN PATENTS 23,211 10/1965 Japan 264-18 39,493 12/1970 Japan 264-182 JAY H. WOOD, Primary Examiner US. Cl. X.R.

260--29.6 AN, 29.6 AQ, 34.2, 898; 264-211 the solid additive UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No- 3,773,884 Dated Novemger 20, .1973

InVentofls) YVUKIO SHIMOSAKA and YOSHIHIRO UNO It is certified that error appears in the above-identified patent and that said' Letters Patent are hereby corrected as shown below:

Column 2, between lines 38 and 39, insert the following:

--fibers thus produced. The present process'also avoids Signed and sealed this lath-da of April 197E.

(SEAL) Attest:

C. MARSHALL DANN EDWARD I LFLETCHERJR. Attesting Officer Commissioner of Patents r PC4050 (10-69) 

